Space vehicles, such as, for example, the space shuttles, require protective exterior thermal insulation to facilitate leaving and re-entering the Earth's atmosphere. For example, during re-entry, to be effective, exterior insulation must maintain the vehicle's external structure temperature below about 350° F., while simultaneously experiencing external thermal environments in excess of about 1830° F. In addition, the same external thermal protection must insulate the vehicle, including the external structure, from severe cold found in outer space (e.g. temperature of less than about −100° F.). Still further, external thermal protective elements must withstand the mechanical stress associated with launch vibrations, acoustics, landing impacts and exposure to radiation.
Previously, lightweight ceramic state-of the art thermal insulation tiles were limited in their use to temperatures of about 2375° F. in an oxidizing environment. If temperatures will exceed 2375° F., a dense ceramic material must be used. However, denser materials add significant, undesirable weight. U.S. Pat. No. 6,225,248 (the '248 patent) discloses a lightweight, high temperature ceramic insulation comprising carbon, silicon and oxygen that is capable of retaining its shape and strength when exposed to temperatures of about 3100° F. The '248 patent further discloses that the improved insulation is made by combining substrates with a reaction product derived from the reaction of di- and tri-functional silanes to form a gel, followed by heating or pyrolyzing the gel and the carbon substrate in an inert environment to form the high temperature, lightweight ceramic insulation.